3D Lattice design elements and mechanical responses
Compliant 3D lattice structures open a world of possibilities for product design. These structures, made from additively manufactured elastomer, are highly deformable, and their mechanical properties can be tuned over a wide range of responses.
Designing compliant lattice structures requires expertise and the right software tools. At Fast Radius, we’ve designed and tested thousands of lattices for dozens of different products and applications. Over time we created a large library that classifies lattice geometry, types, mechanical properties, and manufacturability.
Here we show four compliant lattice structures from our library. These are simple examples that illustrate how design elements affect mechanical responses.
Key design elements for elastomer lattice structures
Four elements are commonly considered in the design of elastomer lattice structures.
First, the geometry of the lattice refers to the physical size and shape of the lattice components and how they are arrayed in a pattern throughout the structure. A repeat unit is known as a unit cell. Many lattice geometries are inspired by cellular or crystal structures seen in nature.
Second, the stiffness or modulus of the lattice is the force required to deform the structure. The modulus is typically defined for small deformations, when the lattice response is fully elastic.
Third, the buckling response describes the way the lattice structure yields. The buckling response of a lattice structure depends upon structural instability of lattice elements as they deform. Not all lattice structures exhibit buckling, and buckling is not always desired.
Finally, energy dissipation is the ability of the structure to absorb energy while it is being deformed.
Simple Cubic lattice
This Simple Cubic lattice has unit cell size 7.5 mm and truss width 2 mm. The modulus is 0.72 MPa.
Buckling response: This structure exhibits a buckling instability. After a strain of about 0.05, the modulus is constant at a stress plateau of 25 kPa. Additional deformation does not increase the modulus.
Energy dissipation: The Simple Cubic lattice has an inelastic buckling behavior, which produces a different response when it is being loaded and unloaded. The inelastic behavior can be used for many purposes, including energy dissipation.
Applications: The buckling response of this Simple Cubic lattice produces a force threshold that makes it a good candidate for personal protection applications and shielding sensitive components. This lattice type is effective for filling gaps between components in assemblies.
Kelvin cell lattice
This Kelvin cell lattice has unit cell size 10 mm and truss width 2 mm. The modulus is 0.44 MPa.
Buckling response: Unlike the Simple Cubic lattice, the Kelvin cell lattice structure has a low buckling point, meaning its beams stretch in response to force. The Kelvin cell lattice does not have a plateau and compresses continuously with a simple elastic stiffness until it is fully compacted.
Energy dissipation: The Kelvin cell lattice stores energy with its elastic deformation, and it returns to its original shape quickly—like a spring—when force is removed.
Applications: The Kelvin cell lattice makes a good candidate for foam replacement in products under static compression like seat cushions or body pads. With its intricate hexagonal cells, the Kelvin cell lattice is quite striking, making it a good option for aesthetic and fashion applications.
This Body-Centered lattice has unit cell size 10 mm and truss width 2 mm. The modulus is 0.07 MPa.
Buckling response: The Body-Centered lattice structure has a stretching response, meaning it responds with increasing force per unit displacement until fully compacted. The modulus is much lower compared to the Simple Cubic lattice, and it does not have a plateau stress.
Energy dissipation: Like the Kelvin unit, the Body-Centered lattice stores energy with its elastic deformation and returns to its original shape quickly—like a spring—when force is removed.
Applications: With its high strain elastic response, the Body-Centered lattice makes a good candidate for foam replacement in products under static compression. The angled struts pointing towards the center of the cell make its response even and consistent.
Body-Centered Cubic (BCC) lattice
The Body-Centered Cubic lattice combines the Body-Centered and Simple Cubic lattices in a single structure. This lattice has unit cell size 7.5 mm, truss width 1 mm. The modulus is 0.23 MPa, higher than the Simple Cubic and Body-Centered Cubic lattices above.
Buckling response: Since the BCC lattice combines two types of lattices, its response is a combination of both. This lattice buckles like the Simple Cubic lattice with a plateau stress (0.12 MPa), but it has a more stable post-buckling behavior.
Energy dissipation: Because this lattice combines both elastic and buckling response, it is possible to adjust energy storage and dissipation to serve specific applications.
Applications: The BCC lattice is good for applications that benefit from a tailored elastic and buckling response. It also works well when a product requires energy dissipation with a more stable response than the pure buckling seen in the Simple Cubic lattice.
The four structures highlighted in this article only scratch the surface of what’s possible with elastomeric lattice design. If you want to learn more about how to incorporate lattice design in your next project, contact the experts at Fast Radius.